The challenges of classical galactosemia: HRQoL in pediatric and adult patients

BACKGROUND

Classical galactosemia (CG), an inborn error of galactose metabolism, results in long-term complications including cognitive impairment and movement disorders, despite early diagnosis and dietary treatment. Two decades ago, lower motor-, cognitive- and social health related quality of life (HRQoL) was demonstrated in pediatric and adult patients. Since then, the diet has been relaxed, newborn screening was implemented and new international guidelines resulted in major changes in follow-up. The aim of this study was to assess HRQoL of CG by means of online self- and/or proxy-HRQoL-questionnaires focusing on the main areas of concern of CG (i.e. anxiety, depression, cognition, fatigue, social- and upper extremity function) within the patient-reported outcomes measurement information system (PROMIS®) and generic HRQoL-questionnaires (TAPQOL, TACQOL, TAAQOL).

RESULTS

Data of 61 Dutch patients (aged 1-52 years) were collected and compared to available Dutch or US reference populations. On the PROMIS-questionnaires, children reported more fatigue (P = 0.044), lower function in upper extremities (P = 0.021), more cognitive difficulties (P = 0.055, d = 0.56) and higher anxiety (P = 0.063, d = 0.52) than reference children although the latter findings remained non-significant. Parents of CG patients reported lower quality of peer relationships of their children (P < 0.001). Both children and parents reported lower cognitive functioning (P = 0.005, P = 0.010) on the TACQOL. Adults reported on PROMIS domains lower cognitive functioning (P = 0.030), higher anxiety (P = 0.004) and more fatigue (P = 0.026). Cognitive difficulties were reported on the TAAQOL by adults (P < 0.001), as well as physical-, sleeping and social difficulties.

CONCLUSIONS

CG remains to impact the HRQoL of pediatric and adult patients negatively on several domains including cognition, anxiety, motor function and fatigue. A lower social health was mainly reported by parents, and not by patients themselves. The Covid-19 pandemic might have amplified the results on anxiety although higher levels of anxiety fit pre-pandemic findings. The reported fatigue is a new finding in CG. Because the effect of lockdown fatigue could not be eliminated and fatigue is a frequent finding in patients with chronic disorders, future studies are warranted. Clinicians and researchers should be attentive to both pediatric and adult patients, and the age-dependent difficulties they might encounter.

The hypergonadotropic hypogonadism conundrum of classic galactosemia

BACKGROUND

Hypergonadotropic hypogonadism is a burdensome complication of classic galactosemia (CG), an inborn error of galactose metabolism that invariably affects female patients. Since its recognition in 1979, data have become available regarding the clinical spectrum, and the impact on fertility. Many women have been counseled for infertility and the majority never try to conceive, yet spontaneous pregnancies can occur. Onset and mechanism of damage have not been elucidated, yet new insights at the molecular level are becoming available that might greatly benefit our understanding. Fertility preservation options have expanded, and treatments to mitigate this complication either by directly rescuing the metabolic defect or by influencing the cascade of events are being explored.

OBJECTIVE AND RATIONALE

The aims are to review: the clinical picture and the need to revisit the counseling paradigm; insights into the onset and mechanism of damage at the molecular level; and current treatments to mitigate ovarian damage.

SEARCH METHODS

In addition to the work on this topic by the authors, the PubMed database has been used to search for peer-reviewed articles and reviews using the following terms: 'classic galactosemia', 'gonadal damage', 'primary ovarian insufficiency', 'fertility', 'animal models' and 'fertility preservation' in combination with other keywords related to the subject area. All relevant publications until August 2022 have been critically evaluated and reviewed.

OUTCOMES

A diagnosis of premature ovarian insufficiency (POI) results in a significant psychological burden with a high incidence of depression and anxiety that urges adequate counseling at an early stage, appropriate treatment and timely discussion of fertility preservation options. The cause of POI in CG is unknown, but evidence exists of dysregulation in pathways crucial for folliculogenesis such as phosphatidylinositol 3-kinase/protein kinase B, inositol pathway, mitogen-activated protein kinase, insulin-like growth factor-1 and transforming growth factor-beta signaling. Recent findings from the GalT gene-trapped (GalTKO) mouse model suggest that early molecular changes in 1-month-old ovaries elicit an accelerated growth activation and burnout of primordial follicles, resembling the progressive ovarian failure seen in patients. Although data on safety and efficacy outcomes are still limited, ovarian tissue cryopreservation can be a fertility preservation option. Treatments to overcome the genetic defect, for example nucleic acid therapy such as mRNA or gene therapy, or that influence the cascade of events are being explored at the (pre-)clinical level.

WIDER IMPLICATIONS

Elucidation of the molecular pathways underlying POI of any origin can greatly advance our insight into the pathogenesis and open new treatment avenues. Alterations in these molecular pathways might serve as markers of disease progression and efficiency of new treatment options.

Qualitative interviews with adults with Classic Galactosemia and their caregivers: disease burden and challenges with daily living

BACKGROUND

Classic Galactosemia is a rare, autosomal recessive disease in which galactose is not metabolized properly due to severe deficiency/absence of the galactose-1-phosphate uridylyltransferase (GALT) enzyme, converting to an aberrant and toxic metabolite, galactitol. Newborn screening and timely galactose-restricted diet can resolve acute symptoms and decrease fatalities. However, despite this, significant chronic, progressive morbidities remain which have a real impact upon daily life. To better understand the burden of disease, 20 in-depth qualitative interviews were undertaken with adult patients (n = 12), and their caregivers (n = 8), enrolled in the ACTION-Galactosemia trial, part of a clinical program designed to investigate the safety and efficacy of AT-007 (govorestat) in reducing toxic galactitol and long-term clinical outcomes in Classic Galactosemia.

RESULTS

Interviews revealed the substantial burden of Classic Galactosemia on patients and families. Most adults were not able to live independently, and all required support with day-to-day activities. Short- and long-term memory difficulties and tremors were identified as the most frequently experienced and challenging symptoms. Other difficulties such as fine motor skills and slow/slurred speech contribute to the significant impact on daily activities, affecting ability to communicate and interact with others. Symptoms were first noticed in early childhood and worsened with age. Classic Galactosemia impacted all areas of daily functioning and quality of life, leading to social isolation, anxiety, anger/frustration and depression. This demonstrates the significant burden of disease and challenges associated with Classic Galactosemia.

CONCLUSIONS

The impact on both patients and caregivers underscores the severity of the unmet medical need and the importance of pharmacological intervention to halt or prevent disease progression. Any treatment that could reduce symptoms or slow functional decline would ease the burden of this condition on patients and caregivers.

Transient developmental delays in infants with Duarte-2 variant galactosemia

Duarte galactosemia is not classic galactosemia, but rather an example of biochemical variant galactosemia that results in approximately 25% residual activity of galactose-1-phosphate uridylyltransferase (GALT) enzyme. In contrast, classic galactosemia is associated with complete or near complete absence of GALT activity. While infants with classic galactosemia are placed on galactose-restricted diets to prevent the acute and long-term manifestations of their metabolic disorder, while individuals with Duarte variant galactosemia (Duarte-2 galactosemia) do not require diet therapy. The long-term complications that are seen in classic galactosemia such as cerebellar ataxia, and hypergonadotropic hypogonadism do not occur in Duarte-2 galactosemia. While Duarte galactosemia does not appear to be a metabolic disease, it may have an impact on early neurodevelopmental outcomes. This study examined developmental outcomes and the need for special services in individuals with Duarte-2 galactosemia in comparison to individuals with classic galactosemia. We performed a medical record review of individuals with GALT deficiency who were evaluated at Boston Children's Hospital and enrolled in our study of outcomes in galactosemia. This included 95 participants, 21 with Duarte-2 galactosemia and 73 with classic galactosemia. Duarte-2 participants had developmental test scores within the average range. However, 42% of subjects with Duarte-2 galactosemia had participated in early intervention and/or special education and 32% received speech therapy. Their pattern of strengths and weaknesses in cognitive/language/motor domains was similar to that noted in participants with classic galactosemia, albeit to a milder degree. The data indicate that in children with Duarte-2 variant galactosemia, the cognitive/language and motor skills were within normal limits with their cognitive/language skills developing earlier than their motor skills during their first year of life. A history of diet treatment was not related to the use of special services. These results suggest that Duarte-2 galactosemia increases the risk for early mild developmental delays irrespective of treatment history, which resolves over time, and highlights the need to further assess neurodevelopment in early infancy, in Duarte-2 galactosemia. As Duarte-2 galactosemia is not a bona fide biochemical genetic disease, we hypothesize that elements in the genomic space that include the GALT gene are responsible for a transient delay in language-related motor skills during early infancy.

Gray and white matter are both affected in classical galactosemia: An explorative study on the association between neuroimaging and clinical outcome

BACKGROUND

Classical Galactosemia (CG) is an inherited disorder of galactose metabolism caused by a deficiency of the galactose-1-phosphate uridylyltransferase (GALT) enzyme resulting in neurocognitive complications. As in many Inborn Errors of Metabolism, the metabolic pathway of CG is well-defined, but the pathophysiology and high variability in clinical outcome are poorly understood. The aim of this study was to investigate structural changes of the brain of CG patients on MRI and their association with clinical outcome.

METHODS

In this prospective cohort study an MRI protocol was developed to evaluate gray matter (GM) and white matter (WM) volume of the cerebrum and cerebellum, WM hyperintensity volume, WM microstructure and myelin content with the use of conventional MRI techniques, diffusion tensor imaging (DTI) and quantitative T1 mapping. The association between several neuroimaging parameters and both neurological and intellectual outcome was investigated.

RESULTS

Twenty-one patients with CG (median age 22 years, range 8-47) and 24 controls (median age 30, range 16-52) were included. Compared to controls, the WM of CG patients was lower in volume and the microstructure of WM was impaired both in the whole brain and corticospinal tract (CST) and the lower R1 values of WM, GM and the CST were indicative of less myelin. The volume of WM lesions were comparable between patients and controls. The 9/16 patients with a poor neurological outcome (defined as the presence of a tremor and/or dystonia), demonstrated a lower WM volume, an impaired WM microstructure and lower R1 values of the WM indicative of less myelin content compared to 7/16 patients without movement disorders. In 15/21 patients with a poor intellectual outcome (defined as an IQ < 85) both GM and WM were affected with a lower cerebral and cerebellar WM and GM volume compared to 6/21 patients with an IQ ≥ 85. Both the severity of the tremor (as indicated by the Tremor Rating Scale) and IQ (as continuous measure) were associated with several neuroimaging parameters such as GM volume, WM volume, CSF volume, WM microstructure parameters and R1 values of GM and WM.

CONCLUSION

In this explorative study performed in patients with Classical Galactosemia, not only WM but also GM pathology was found, with more severe brain abnormalities on MRI in patients with a poor neurological and intellectual outcome. The finding that structural changes of the brain were associated with the severity of long-term complications indicates that quantitative MRI techniques could be of use to explain neurological and cognitive dysfunction as part of the disease spectrum. Based on the clinical outcome of patients, the absence of widespread WM lesions and the finding that both GM and WM are affected, CG could be primarily a GM disease with secondary damage to the WM as a result of neuronal degeneration. To investigate this further the course of GM and WM should be evaluated in longitudinal research, which could also clarify if CG is a neurodegenerative disease.

Deep phenotyping classical galactosemia: clinical outcomes and biochemical markers

Early diagnosis and dietary treatment do not prevent long-term complications, which mostly affect the central nervous system in classical galactosemia patients. The clinical outcome of patients is highly variable, and there is an urgent need for prognostic biomarkers. The aim of this study was first to increase knowledge on the natural history of classical galactosemia by studying a cohort of patients with varying geno- and phenotypes and second to study the association between clinical outcomes and two possible prognostic biomarkers. In addition, the association between abnormalities on brain MRI and clinical outcomes was investigated. Classical galactosemia patients visiting the galactosemia expertise outpatient clinic of the Amsterdam University Medical Centre were evaluated according to the International Classical Galactosemia guideline with the addition of an examination by a neurologist, serum immunoglobulin G N-glycan profiling and a brain MRI. The biomarkers of interest were galactose-1-phosphate levels and N-glycan profiles, and the clinical outcomes studied were intellectual outcome and the presence or absence of movement disorders and/or primary ovarian insufficiency. Data of 56 classical galactosemia patients are reported. The intellectual outcome ranged from 45 to 103 (mean 77 ± 14) and was <85 in 62%. Movement disorders were found in 17 (47%) of the 36 tested patients. In females aged 12 years and older, primary ovarian insufficiency was diagnosed in 12 (71%) of the 17 patients. Significant differences in N-glycan peaks were found between controls and patients. However, no significant differences in either N-glycans or galactose-1-phosphate levels were found between patients with a poor (intellectual outcome < 85) and normal intellectual outcome (intellectual outcome ≥ 85), and with or without movement disorders or primary ovarian insufficiency. The variant patients detected by newborn screening, with previously unknown geno- and phenotypes and currently no long-term complications, demonstrated significantly lower galactose-1-phospate levels than classical patients (P < 0.0005). Qualitative analysis of the MRI's demonstrated brain abnormalities in 18 of the 21 patients, more severely in patients with a lower intellectual outcome and/or with movement disorders. This study demonstrates a large variability in clinical outcome, which varies from a below average intelligence, movement disorders and in females primary ovarian insufficiency to a normal clinical outcome. In our cohort of classical galactosemia patients, galactose-1-phosphate levels and N-glycan variations were not associated with clinical outcomes, but galactose-1-phosphate levels did differentiate between classical and variant patients detected by newborn screening. The correlation between brain abnormalities and clinical outcome should be further investigated by quantitative analysis of the MR images. The variability in clinical outcome necessitates individual and standardized evaluation of all classical galactosemia patients.

Nucleotide sugar profiles throughout development in wildtype and galt knockout zebrafish

Nucleotide sugars (NS) are fundamental molecules in life and play a key role in glycosylation reactions and signal conduction. Several pathways are involved in the synthesis of NS. The Leloir pathway, the main pathway for galactose metabolism, is crucial for production of uridine diphosphate (UDP)-glucose and UDP-galactose. The most common metabolic disease affecting this pathway is galactose-1-phosphate uridylyltransferase (GALT) deficiency, that despite a lifelong galactose-restricted diet, often results in chronically debilitating complications. Alterations in the levels of UDP-sugars leading to galactosylation abnormalities have been hypothesized as a key pathogenic factor. However, UDP-sugar levels measured in patient cell lines have shown contradictory results. Other NS that might be affected, differences throughout development, as well as tissue specific profiles have not been investigated. Using recently established UHPLC-MS/MS technology, we studied the complete NS profiles in wildtype and galt knockout zebrafish (Danio rerio). Analyses of UDP-hexoses, UDP-hexosamines, CMP-sialic acids, GDP-fucose, UDP-glucuronic acid, UDP-xylose, CDP-ribitol, and ADP-ribose profiles at four developmental stages and in tissues (brain and gonads) in wildtype zebrafish revealed variation in NS levels throughout development and differences between examined tissues. More specifically, we found higher levels of CMP-N-acetylneuraminic acid, GDP-fucose, UDP-glucuronic acid, and UDP-xylose in brain and of CMP-N-glycolylneuraminic acid in gonads. Analysis of the same NS profiles in galt knockout zebrafish revealed no significant differences from wildtype. Our findings in galt knockout zebrafish, even when challenged with galactose, do not support a role for abnormalities in UDP-glucose or UDP-galactose as a key pathogenic factor in GALT deficiency, under the tested conditions.

Galactose 1-phosphate accumulates to high levels in galactose-treated cells due to low GALT activity and absence of product inhibition of GALK

Classic Galactosaemia is a genetic disorder, characterised by galactose intolerance in newborns. It occurs due to recessive mutations in the galactose-1-phosphate uridylyltransferase (GALT) gene. One of the main alterations caused by GALT deficiency is the accumulation of galactose 1-phosphate (Gal-1P) in cells. Studies have suggested that Gal-1P exerts cellular toxicity, possibly by inhibiting cellular metabolism. However, the exact significance of Gal-1P in disease pathogenesis remains unclear. In this study, we tested the hypothesis that Gal-1P inhibits cellular glucose utilisation by competing with substrates in the glycolytic pathway. We also investigated the metabolism of both galactose and glucose in GALT-expressing HEK293T and 143B cells to identify critical reactions steps contributing to the metabolic toxicity of galactose. Notably, we found that galactose-treated HEK293T and 143B cells, which express endogenous GALT, accumulate markedly high intracellular Gal-1P concentrations. Despite very high intracellular Gal-1P concentrations, no inhibition of cellular glucose uptake and no significant changes in the intracellular concentrations of glycolytic metabolites were observed. This indicates that Gal-1P does not exert an inhibitory effect on glycolysis in cells and rules out one potential hypothesis for cellular Gal-1P toxicity. We also investigated the mechanism responsible for the observed Gal-1P accumulation. Our results suggest that Gal-1P accumulation is a result of both low GALT activity and the absence of product inhibition by Gal-1P on galactokinase (GALK1), the enzyme responsible for phosphorylating galactose to Gal-1P. These findings provide a better understanding of the disease mechanisms underlying Classic Galactoaemia.

The Galactose Index measured in fibroblasts of GALT deficient patients distinguishes variant patients detected by newborn screening from patients with classical phenotypes

BACKGROUND

The high variability in clinical outcome of patients with Classical Galactosemia (CG) is poorly understood and underlines the importance of prognostic biomarkers, which are currently lacking. The aim of this study was to investigate if residual galactose metabolism capacity is associated with clinical and biochemical outcomes in CG patients with varying geno- and phenotypes.

METHODS

Galactose Metabolite Profiling (GMP) was used to determine residual galactose metabolism in fibroblasts of CG patients. The association between the galactose index (GI) defined as the ratio of the measured metabolites [U¹³C]Gal-1-P/ [¹³C₆]UDP-galactose, and both intellectual and neurological outcome and galactose-1-phosphate (Gal-1-P) levels was investigated.

RESULTS

GMP was performed in fibroblasts of 28 patients and 3 control subjects. The GI of the classical phenotype patients (n = 22) was significantly higher than the GI of four variant patients detected by newborn screening (NBS) (p = .002), two homozygous p.Ser135Leu patients (p = .022) and three controls (p = .006). In the classical phenotype patients, 13/18 (72%) had a poor intellectual outcome (IQ < 85) and 6/12 (50%) had a movement disorder. All the NBS detected variant patients (n = 4) had a normal intellectual outcome (IQ ≥ 85) and none of them has a movement disorder. In the classical phenotype patients, there was no significant difference in GI between patients with a poor and normal clinical outcome. The NBS detected variant patients had significantly lower GI levels and thus higher residual galactose metabolism than patients with classical phenotypes. There was a clear correlation between Gal-1-P levels in erythrocytes and the GI (p = .001).

CONCLUSIONS

The GI was able to distinguish CG patients with varying geno- and phenotypes and correlated with Gal-1-P. The data of the NBS detected variant patients demonstrated that a higher residual galactose metabolism may result in a more favourable clinical outcome. Further research is needed to enable individual prognostication and treatment in all CG patients.

Classical galactosemia: neuropsychological and psychosocial functioning beyond intellectual abilities

Background

Despite early diagnosis and treatment, Classical Galactosemia (CG) patients frequently develop long-term complications, such as cognitive impairment. Available literature primarily reports on general intellectual abilities and shows a substantially lower Full Scale Intelligence Quotient (FSIQ) in CG patients than in the general population. Both problems in social functioning as well as internalizing problems are often reported in CG patients. The combination of intelligence, cognitive functioning, behavior and social functioning has not been studied systematically in CG patients.

Methods

To determine if CG patients demonstrate a specific neuropsychological and psychosocial profile, we investigated intelligence, functioning on multiple cognitive domains, behavior and social functioning with a comprehensive neuropsychological test battery and questionnaires (self- and proxy-reported).

Results

The data of 48 patients, aged 4–47 years are reported. FSIQ ranged from 45 to 103 (mean 77 ± 14). A negative correlation between age and FSIQ was demonstrated (p = 0.037) which resulted directly from the inclusion of four young ‘milder’ patients detected by newborn screening (NBS) with an expected better clinical outcome. Compared to normative data, patients had significantly lower but highly variable scores on all cognitive domains, especially on tests requiring mental speed. In the context of the FSIQ, 43% of the cognitive test results exceeded IQ based expectations. Overall, the patients’ scores on social functioning were in the normal range but internalizing problems were frequently reported. In our cohort, an early initiation of dietary treatment due to NBS or family screening did not result in a more favorable neuropsychological outcome.

Conclusions

In this study, we demonstrated that as a cohort, CG patients have a below average intelligence and impaired cognitive functioning without a distinctive neuropsychological profile. The effect of age on neurocognitive functioning should be assessed in longitudinal studies. Social functioning was not impaired, but patients may be at risk for internalizing problems. Considering the large variability in cognitive, behavioral and social functioning and the finding that cognitive outcomes may exceed IQ based expectations, an individual evaluation and follow-up is warranted in all CG patients to ensure timely support if needed.

Cognitive functioning in patients with classical galactosemia: a systematic review

Background

Patients with the metabolic disorder classical galactosemia suffer from long-term complications despite a galactose-restricted diet, including a below average intelligence level. The aim of the current review was to investigate the incidence and profile of cognitive impairments in patients with classical galactosemia.

Method

MEDLINE, EMBASE and PsychINFO were searched up to 23 October 2018 for studies examining information processing speed, attention, memory, language, visuospatial functioning, executive functioning and social cognition in patients with confirmed classical galactosemia utilizing standardized neuropsychological tests. Data synthesis followed a narrative approach, since the planned meta-analysis was not possible due to large variability between the neuropsychological assessments.

Results

Eleven studies were included, including case-studies. The quality of most studies was moderate to low. As a group, patients with classical galactosemia exhibit below average to low scores on all cognitive domains. A large proportion of the patients perform on an impaired level on attention, memory and vocabulary. Evidence for impairments in information processing speed, language, visuospatial functioning and aspects of executive functioning was limited due to the small number of studies investigating these cognitive functions. Social cognition was not examined at all.

Conclusions

Given the moderate to low quality of the included studies and the limited evidence in many cognitive domains, the incidence of cognitive impairment in patients with classical galactosemia is not yet clear. Both clinicians and researchers encountering patients with classical galactosemia need to be aware of possible cognitive impairments. Future well-designed studies are needed to determine the cognitive profile of classical galactosemia. This can be the basis for the development of intervention strategies.

Functional analysis of GALT variants found in classic galactosemia patients using a novel cell-free translation method

Classic galactosemia is an autosomal recessive disorder caused by deleterious variants in the galactose-1-phosphate uridylyltransferase (GALT) gene. GALT enzyme deficiency leads to an increase in the levels of galactose and its metabolites in the blood causing neurodevelopmental and other clinical complications in affected individuals. Two GALT variants NM_000155.3:c.347T>C (p.Leu116Pro) and NM_000155.3:c.533T>G (p.Met178Arg) were previously detected in Filipino patients. Here, we determine their functional effects on the GALT enzyme through in silico analysis and a novel experimental approach using a HeLa-based cell-free protein expression system. Enzyme activity was not detected for the p.Leu116Pro protein variant, while only 4.5% of wild-type activity was detected for the p.Met178Arg protein variant. Computational analysis of the variants revealed destabilizing structural effects and suggested protein misfolding as the potential mechanism of enzymological impairment. Biochemical and computational data support the classification of p.Leu116Pro and p.Met178Arg variants as pathogenic. Moreover, the protein expression method developed has utility for future studies of GALT variants.

The natural history of classic galactosemia: lessons from the GalNet registry

BACKGROUND

Classic galactosemia is a rare inborn error of carbohydrate metabolism, caused by a severe deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). A galactose-restricted diet has proven to be very effective to treat the neonatal life-threatening manifestations and has been the cornerstone of treatment for this severe disease. However, burdensome complications occur despite a lifelong diet. For rare diseases, a patient disease specific registry is fundamental to monitor the lifespan pathology and to evaluate the safety and efficacy of potential therapies. In 2014, the international Galactosemias Network (GalNet) developed a web-based patient registry for this disease, the GalNet Registry. The aim was to delineate the natural history of classic galactosemia based on a large dataset of patients.

METHODS

Observational data derived from 15 countries and 32 centers including 509 patients were acquired between December 2014 and July 2018.

RESULTS

Most affected patients experienced neonatal manifestations (79.8%) and despite following a diet developed brain impairments (85.0%), primary ovarian insufficiency (79.7%) and a diminished bone mineral density (26.5%). Newborn screening, age at onset of dietary treatment, strictness of the galactose-restricted diet, p.Gln188Arg mutation and GALT enzyme activity influenced the clinical picture. Detection by newborn screening and commencement of diet in the first week of life were associated with a more favorable outcome. A homozygous p.Gln188Arg mutation, GALT enzyme activity of ≤ 1% and strict galactose restriction were associated with a less favorable outcome.

CONCLUSION

This study describes the natural history of classic galactosemia based on the hitherto largest data set.

The ability of an LC-MS/MS-based erythrocyte GALT enzyme assay to predict the phenotype in subjects with GALT deficiency

BACKGROUND

GALT deficiency is a rare genetic disorder of carbohydrate metabolism. Due to the decreased activity or absence of the enzyme galactose-1-phosphate uridylyltransferase (GALT), cells from affected individuals are unable to metabolize galactose normally. Lactose consumption in the newborn period could potentially lead to a lethal disease process with multi-organ involvement. In contrast to the newborn-stage disease, however, a galactose-restricted diet does not prevent long-term complications such as central nervous system (CNS) dysfunction with speech defects, learning disability and neurological disease in addition to hypergonadotropic hypogonadism or primary ovarian insufficiency (POI) in females. As the literature suggests an association between GALT enzyme activity and the long-term complications, it is of importance to have a highly sensitive assay to quantify the GALT enzyme activity. To that end, we had developed a sensitive and accurate LC-MS/MS method to measure GALT enzyme activity. Its ability to predict outcome is the subject of this report.

MATERIALS AND METHODS

The GALT enzyme activity in erythrocytes from 160 individuals, in which 135 with classic, clinical variant or biochemical variant galactosemia, was quantified by LC-MS/MS. Individuals with GALT deficiency were evaluated for the long-term complications of speech defects, dysarthria, ataxia, dystonia, tremor, POI, as well as intellectual functioning (full scale IQ). The LC-MS/MS results were compared to a variety of assays: radioactive, [¹⁴C]-galactose-1-phosphate, paper chromatography with scintillation counting, enzyme-coupled assays with spectrophotometric or fluorometric readout or high-pressure liquid chromatography with UV detection of UDP-galactose.

RESULTS

The LC-MS/MS method measured GALT activity as low as 0.2%, whereas other methods showed no detectable activity. Largely due to GALT activities that were over 1%, the LC-MS/MS measurements were not significantly different than values obtained in other laboratories using other methodologies. Severe long-term complications were less frequently noted in subjects with >1% activity. Patients with a p.Q188R/p.Q188R genotype have no residual enzyme activity in erythrocytes.

CONCLUSION

Our LC-MS/MS assay may be necessary to accurately quantify residual GALT activities below 5%. The data suggest that patients with >1% residual activity are less likely to develop diet-independent long-term complications. However, much larger sample sizes are needed to properly assess the clinical phenotype in patients with residual enzyme activities between 0.1 and 5%.

Fertility in adult women with classic galactosemia and primary ovarian insufficiency

OBJECTIVE

To study pregnancy chance in adult women with classic galactosemia and primary ovarian insufficiency. Despite dietary treatment, >90% of women with classic galactosemia develop primary ovarian insufficiency, resulting in impaired fertility. For many years, chance of spontaneous conception has not been considered, leading to counseling for infertility. But an increasing number of reports on pregnancies in this group questions whether current counseling approaches are correct.

DESIGN

Multicenter retrospective observational study.

SETTING

Metabolic centers.

PATIENT(S)

Adult women (aged >18 y) with confirmed classic galactosemia and primary ovarian insufficiency were included.

INTERVENTION(S)

Participants and medical records were consulted to obtain study data in a standardized manner with the use of a questionnaire.

MAIN OUTCOME MEASURE(S)

Conception opportunities, time to pregnancy, pregnancy outcome, hormone replacement therapy use, fertility counseling, and the participants' vision of fertility were evaluated. Potential predictive factors for increased pregnancy chance were explored.

RESULT(S)

Eighty-five women with classic galactosemia and primary ovarian insufficiency participated. Twenty-one women actively attempted to conceive or did not take adequate contraceptive precautions. Of these 21 women, nine became pregnant spontaneously (42.9%). This was higher than reported in primary ovarian insufficiency due to other causes (5%-10%). After a period of 12 months, a cumulative proportion of 27.8% of couples had conceived, which increased to 48.4% after 24 months and 61.3% after 27 months. Predictive factors could not be identified. A considerable miscarriage rate of 30% was observed (6 of 20 pregnancies). Although a substantial proportion of women expressed a child-wish (n = 28/53; 52.8%), the vast majority of participants (n = 43/57; 75.4%) considered conceiving to be highly unlikely, owing to negative counseling in the past.

CONCLUSION(S)

The pregnancy rate in women with classic galactosemia and primary ovarian insufficiency was higher than for women with primary ovarian insufficiency of any cause. This shifting paradigm carries significant implications for fertility counseling and potential application of fertility preservation techniques.

Bone Health in Classic Galactosemia: Systematic Review and Meta-Analysis

INTRODUCTION

Previous studies have reported an association between classic galactosemia (CG) and decreased bone mass. The primary objective of this systematic review with meta-analysis was to determine the extent of bone mineral density (BMD) Z-score reduction. Low BMD was defined as a Z-score ≤-2 standard deviations (SD). The secondary objective was to evaluate other indicators of bone status through a descriptive analysis.

METHODS

Systematic search strategies were developed by an experienced clinical librarian. Selection of relevant manuscripts, risk of bias assessment, and data extraction were performed independently by two investigators.

RESULTS

Four studies were included in the meta-analysis. BMD Z-scores in children and adults with CG measured at the lumbar spine (LBMD; 4 studies; n  = 112), total hip (HBMD; 2 studies; n = 58), and femoral neck (FBMD; 2 studies; n = 73) were assessed. Mean BMD Z-scores in the CG population were LBMD -0.70 (95% CI: -0.88, -0.52); HBMD -0.89 (95% CI: -1.14, -0.64); and FBMD -0.63 (95% CI -1.29, 0.02). Results from studies included in the descriptive analysis (n = 7) show that vitamin D levels were frequently in the low reference range, whereas serum calcium levels were within reference range.

CONCLUSION

The mean BMD Z-score in the CG population is -0.7, which is lower than in the general population, though still within two SD of the reference mean of zero. This indicates that bone health is mildly affected in CG and that more patients, compared to the general population, are at risk for a BMD Z-score ≤-2 SD. In conclusion, clinicians should ensure appropriate preventive and therapeutic measures for CG patients.